The boiler works for a while, then switches itself off. You can restart it (see the user guide below) but this begins to happen more and more frequently.
The boiler is developing a problem with the electronic printed curcuit board (PCB) that controls it. (There can be other, but related causes.)
What you can do
Nothing yourself. Get an expert to fix it. See the note on the general Heating page re Potterton’s own repair service.
You may like to read this Foggy Log blog item.
Here is the Suprima User Guide (pdf 500Kb Right-click and ‘Save As…’ to download)